Peel Test for Cathode Materials of Lithium-Ion Batteries in a Thermostatic Chamber

Significance of the Topic

Lithium-ion battery performance largely depends on the adhesion strength between cathode active materials and current collectors. Precise evaluation of adhesion under varying temperatures enables optimization of electrode manufacturing, preventing delamination and electrical performance loss.

Objectives and Study Overview

This study aimed to assess temperature-dependent adhesion strength of lithium iron phosphate cathode materials using a peel test within a thermostatic chamber. Emphasis was placed on replicating real battery operating conditions.

Used Instrumentation

• Precision Universal Testing Machine AGS-V with 1 kN screw-type flat grips
• Compact Thermostatic Chamber TCE-N300A
• Copper foil peeling test device
• Load cell (capacity 500 N) with enhanced accuracy range
• TRAPEZIUM X-V software

Methodology

Rectangular specimens comprised aluminum plates covered with double-sided tape and coated with lithium iron phosphate binder. Each sample's aluminum foil was peeled at 90° relative to the specimen. Tests were conducted at room temperature, 50 °C, and 70 °C with a crosshead speed of 5 mm/sec, displacement range set to 100 mm, and force data origin at 0.05 N. Three replicates were performed per temperature.

Main Results and Discussion

Force-displacement curves demonstrated a clear increase in adhesion force with temperature. Average adhesion strengths (N) were:

• Room temperature: 0.753
• 50 °C: 0.903
• 70 °C: 8.07

Higher temperature improved polymer binder flow and interfacial contact, leading to increased peel resistance. Consistency across replicates indicates reliable measurement.

Benefits and Practical Applications

• Accurate adhesion data under realistic thermal conditions informs electrode formulation and processing.
• High-precision load cell enables reliable measurements even at low forces.
• Thermostatic testing reveals performance across battery operating temperatures, aiding failure analysis and quality control.

Future Trends and Potential Applications

Integration of peel testing with in situ microscopy or spectroscopy could elucidate failure mechanisms at the micro scale. Expansion to anode materials or various binder chemistries will broaden applicability. Automated high-throughput testing may accelerate electrode optimization in advanced battery development.

Conclusion

The peel test in a controlled temperature environment successfully characterized the adhesion strength of lithium iron phosphate cathodes. Increased temperature enhanced adhesion, underscoring the importance of thermal effects in electrode design. The methodology provides a robust tool for battery material evaluation and optimization.